1. Field of the Invention
The present invention relates to a solid state image sensing device and solid state image sensing device production method, and more specifically relates a solid state image sensing device using semiconductor thin layers laminated on a semiconductor substrate as a photoelectric conversion element, and method for producing said device.
2. Description of the Related Art
Unidimensional solid state image sensing devices for use in facsimile machines, image scanners, and digital copiers and the like, and two-dimensional solid state image sensing devices for use in video cameras have been proposed as solid state image sensing devices in conventional image forming apparatuses.
In recent years, there has been a demand for high resolution images formed by image forming apparatuses using the aforesaid solid state image sensing devices. To satisfy these demands, the picture element size of the solid state image sensing device must be very small. When the size of the picture elements is very small, however, the sensitivity of the solid state image sensing device is insufficient.
Consider a construction of an intensifying layer for intensifying a photocurrent superimposed over a photoreceptor as a construction which eliminates the previously described disadvantages.
U.S. patent application Ser. No. 5,101,255 discloses a unidimensional long sensor comprising a glass substrate on which is superimposed a readout electrode, CeO.sub.2 thin layer as a rectifying contact auxiliary layer, noncrystalline Se layer as a photoconductive layer, and a light-transmitting conductive layer. In this unidimensional long sensor, a non-crystalline Se layer is superimposed over a glass substrate as a photoconductive layer, and a strong electric field is applied to the noncrystalline layer so as to generate a charge intensifying action within the noncrystalline layer, thereby increasing the sensitivity of the noncrystalline layer.
In this unidimensional long sensor, however, the bed of the photoconductive layer is not flat because a readout electrode is provided on the glass substrate. When the bed is not flat as in this example, there is variance generated in the electrical output of the sensor because the layer thickness is nonuniform.
When a semiconductor thin layer is superimposed as in the aforesaid unidimensional long sensor, defects occur in the interface of the laminate portion, which generates dark current and adversely affects voltage resistance characteristics. Furthermore, if the substrate is a semiconductor substrate, an injection current is generated from the substrate.